add alignment to enable store merging in strict-alignment targets

In g++.dg/opt/store-merging-2.C, the natural alignment of types T and
S is a single byte, so we shouldn't expect store merging on
strict-alignment platforms.  Indeed, without something like the
adjust-alignment pass to bump up the alignment of the automatic
variable, as in GCC 10, the optimization does not occur.

This patch adjusts the test so that the required alignment is
expressly stated, and so we don't rely on its accidentally being there
to get the desired optimization.

for  gcc/testsuite/ChangeLog

	* g++.dg/opt/store-merging-2.C: Add the required alignment.

diff --git a/gcc/testsuite/g++.dg/opt/store-merging-2.C b/gcc/testsuite/g++.dg/opt/store-merging-2.C
index 3c17033764b75608dd9e609d2f776f6f7bf8cd4e..b1ad7018a17895bddcae8bb7a2bfa5d8fa8843af 100644 (file)
--- a/gcc/testsuite/g++.dg/opt/store-merging-2.C
+++ b/gcc/testsuite/g++.dg/opt/store-merging-2.C
@@ -4,7 +4,9 @@
 // { dg-options "-O2 -flifetime-dse=2 -fdump-tree-store-merging-details" }
 // { dg-final { scan-tree-dump "New sequence of 2 stores to replace old one of 3 stores" "store-merging" } }
 
-struct T { char a[128]; };
+/* The alignment is necessary for store-merging to take place on
+   strict-alignment targets.  */
+struct __attribute__ ((__aligned__ (4))) T { char a[128]; };
 struct S { S () : a () { a.a[12] = 0; a.a[13] = 1; a.a[14] = 0; a.a[15] = 6; } T a; };
 void foo (S &);
 void bar (void) { S s; foo (s); }